It isn’t clear why some people get asthma and others don’t, but it’s probably due to a combination of environmental and genetic (inherited) factors. Exposure to various irritants and substances that trigger allergies (allergens) can trigger signs and symptoms of asthma. Asthma triggers are different from person to person. Triggers are things like dust mites or pollen that can make asthma symptoms worse.
Sinusitis is usually caused by a virus and often persists even after other upper respiratory symptoms are gone. In some cases, bacteria, or rarely fungus, may cause a sinus infection. Other conditions such as allergies, nasal polyps, and tooth infections can also contribute to sinus pain and symptoms.
Hmm.. I’d say probably a combination of genetic factors and also what you have been exposed to/environmental factors. The environments where we are born and/or live in have a pretty big effect on our general health. You can imagine that if there is a lot of dust, pollution, or lots of plants that make pollen, that it can affect breathing in general.